where \(\mu =\sqrt{\frac{\omega ^2}{\gamma ^2\beta ^2}+q_x^2}\) , and \(h_{n-1}^{(1)}\)  are spherical Hankel functions of the first kind [1]}, which contain \(y^{\prime }\)  in the denominator.
Nevertheless, the final expressions for the Fourier-transformed fields are polynomials in \(y^{\prime }\) , \(z^{\prime }\)  and \(\text{sgn}(y^{\prime })\)  (up to an exponential factor). It follows from the fact that the only singularity of fields \(1/R\)  has spherical symmetry.
Such a structure is preserved after the coordinate substitution (REF ).
